U.S. patent application number 14/431275 was filed with the patent office on 2015-09-10 for multilayered core/shell microcapsules.
This patent application is currently assigned to FIRMENICH SA. The applicant listed for this patent is Firmenich SA. Invention is credited to Gregory Dardelle, Philipp Erni, Marlene Jacquemond.
Application Number | 20150250689 14/431275 |
Document ID | / |
Family ID | 46963565 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150250689 |
Kind Code |
A1 |
Dardelle; Gregory ; et
al. |
September 10, 2015 |
MULTILAYERED CORE/SHELL MICROCAPSULES
Abstract
The invention relates to a method of making multilayer
core/shell microcapsules for delivery of active agents such as
fragrance components of perfume oils. The method includes forming
an outer shell by coacervation surrounding an internal phase which
contains the active agent; and forming an inner shell by
interfacial polymerization at the interface between the internal
phase and the outer shell. The internal phase contains the active
agent. The microcapsules are typically incorporated in a consumer
product wherein the multilayer shell prevents the active agent from
release until desired, generally during use of the consumer
product.
Inventors: |
Dardelle; Gregory; (Geneva,
CH) ; Jacquemond; Marlene; (Geneva, CH) ;
Erni; Philipp; (Geneva, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Firmenich SA |
Geneva 8 |
|
CH |
|
|
Assignee: |
FIRMENICH SA
Geneva 8
CH
|
Family ID: |
46963565 |
Appl. No.: |
14/431275 |
Filed: |
September 13, 2013 |
PCT Filed: |
September 13, 2013 |
PCT NO: |
PCT/EP2013/069681 |
371 Date: |
April 7, 2015 |
Current U.S.
Class: |
510/130 ;
264/4.1; 435/128; 512/4 |
Current CPC
Class: |
A61Q 15/00 20130101;
A61Q 5/12 20130101; A61K 8/73 20130101; B01J 13/10 20130101; A61K
2800/412 20130101; B01J 13/14 20130101; A61K 8/65 20130101; C11D
3/505 20130101; A61K 8/87 20130101; A61Q 5/02 20130101; B01J 13/22
20130101; C11B 9/00 20130101; A61K 8/11 20130101; A61Q 19/10
20130101; B01J 13/16 20130101; A61K 8/84 20130101 |
International
Class: |
A61K 8/11 20060101
A61K008/11; A61K 8/84 20060101 A61K008/84; C11B 9/00 20060101
C11B009/00; A61Q 19/10 20060101 A61Q019/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2012 |
EP |
12185741.1 |
Claims
1. A method of making imerlinked multilayer microcapsules, which
comprises: providing as a dispersion in an aqueous vehicle, a
hydrophobic internal phase comprising a monomer and an active agent
of a fragrancing or flavouring component such as a perfume or
flavour oil; mixing a first and second polvelectrolytes in the
aqueous vehicle under conditions sufficient to form a suspension of
complex coacervate nodules; depositing the complex coacervate
nodules at an interface of an aqueous vehicle adjacent the
hydrophobic internal phase to form an outer shell of the
microcapsule, wherein the hydrophobic internal phase forms the core
and contains the monomer and fragrancing or flavouring component
therein; and introducing a water soluble reactant into the aqueous
vehicle under conditions sufficient to induce interfacial
polymerization of the monomer inside the outer shell to form an
inner shell at the interface between the internal phase and the
outer shell.
2. The method of claim 1, wherein the first polyelectrolyte carries
a net positive charge when the pH is less than 8 while the second
polyelectrolyte carries a net negative charge when the pH is
greater than 2.
3. The method of claim 2, wherein the first polyelectrolyte is
gelatin and the second polyelectrolyte is selected from the group
consisting of carboxymethyl cellulose, sodium carboxymethyl guar
gum, xanthan gum and plant gums.
4. The method of claim 3, wherein the second polyelectrolyte is
acacia gum.
5. The method of claim 1, wherein the monomer is an oil soluble
isocyanate, and the reactant is guanazol, guanidine, or a salt
thereof.
6. The method of claim 1 which further comprises cross-linking the
core-shell capsule chemically or enzymatically before introducing
the reactant into the aqueous vehicle.
7. The method of claim 1, wherein the pH and the temperature of the
aqueous vehicle are adjusted before during or after the
introduction of reactant to control the rate of interfacial
polymerization.
8. The method of claim 1, wherein the microcapsules inner shell has
a volume that is between 0.1 and 80% of the volume of the outer
shell.
9. A multilayered microcapsule produced by the method of claim
1.
10. Multilayer microcapsules comprising an outer shell of a
coacervate, an inner shell of a polymer, and an internal phase
comprising an active agent of a fragrancing or flavouring component
such as a perfume or flavour oil, wherein the inner and outer shell
are present as interlinked layers.
11. The multilayer microcapsules of claim 10, wherein the volume of
the inner shell is between 0.1 and 80% of the volume of the outer
shell.
12. The multilayer microcapsules of claim 11, having a size of
between 5 .mu.m to 1,000 .mu.m.
13. (canceled)
14. A consumer product in the form of a home- or personal-care
product that includes the multilayered microcapsules of claim 9, in
liquid or powder form specifically as a detergent composition, a
fabric softener, a hard surface cleaning composition, a
dishwashing, composition, a shampoo, a hair conditioner, a shower
or bath mousse, oil or gel, a deodorant, or an antiperspirant,
15. A consumer product according to claim 14, comprising from 0.1
to 50% by weight of surfactant.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a delivery system comprising both a
core and a multilayered, composite shell formed by a coacervate and
synthetic polymer, and the use of the delivery system for
encapsulating a liquid, a solid, an emulsion or a dispersion
containing a fragrance or flavor component.
BACKGROUND OF THE INVENTION
[0002] Perfume additives make consumer products such as home and
body care products, and in particular laundry compositions, more
aesthetically pleasing to the consumer and in many cases the
perfume imparts a pleasant fragrance to fabrics treated therewith.
The amount of perfume carryover from an aqueous laundry bath onto
fabrics, however, is often marginal. By encapsulating perfume
additives in microcapsules, the delivery efficiency and active
lifetime of the perfume additives can be improved. Microcapsules
provide several advantages, such as protecting the perfume from
physical or chemical reactions with incompatible ingredients in the
laundry composition, as well as protecting the perfume from
volatilization or evaporation. Microcapsules can be particularly
effective in the delivery and preservation of perfumes in that the
perfumes can be delivered to and retained within the fabric by a
microcapsule that only ruptures, and therefore releases the
perfume, when the fabric is dry. The rupture of microcapsules can
be induced by various factors such as temperature so that the
contents are delivered when the capsule degrades. Alternatively the
microcapsules can be compromised by physical forces, such as
crushing, or other methods that compromise the integrity of the
microcapsules. Additionally, the microcapsule contents may be
delivered via diffusion through the capsule wall during a desired
time interval.
[0003] Scent associated with laundered laundry is important to many
consumers. There are many so called "touch points" that consumers
associated with during the laundry experience. Non-limiting
examples of these touch points include the freshness experience
associated with opening a fabric care container, opening a washing
machine after washing laundry, opening a laundry dryer after drying
laundry, and freshness associated with wearing laundered clothes.
It has been reported that there is a significant portion of
consumers that will fold and put away their laundry about one day
after having laundered laundry. Freshness while folding laundry
about one day after having laundered laundry also signals to the
consumer that the laundry is clean.
[0004] Multilayered capsules are known in the art. US 2005/0112152
generally describes encapsulated fragrance further coated with a
second coating, such as a cationic coating. British patent
application GB 1257178 discloses multicoated capsules produced by
forming a secondary film layer at the interfaces of hydrophilic and
hydrophobic liquids in the defective parts of the already formed
primary film layer, e.g., crackles, capillary micropores or the
like present therein, to fill up the defects.
[0005] British patent application GB 1141186 discloses dual walled
capsules produced by first precoating droplets or solid particles
of an internal phase in an aqueous vehicle through an interfacial
reaction between two reactants, one of which is present in the
aqueous vehicle, the other being present in or on the internal
phase; and then providing another coating by coacervation.
[0006] U.S. Pat. No. 5,180,637 describes double-walled
microcapsules wherein the primary wall is composed of an amino
resin prepared by polycondensation reaction and the secondary wall
is formed by coacervation of a polyion complex of the resin with
polystyrenesulfonic acid or salt thereof, whereby liquid droplets
are deposited on the primary wall. While those microcapsules are
said to have improved resistance to heat and moisture, the
structure of the shell consisting of superposed distinct layers is
likely to delaminate and provide products which are still highly
permeable.
[0007] Fan et al. reports preparing microcapsules with
triallylamine-containing core surrounded by polyelectrolyte shell
of controlled thickness via layer-by-layer assembly technology
("Preparation of oil core/multilayerpolyelectrolyte shell
microcapsules by a coacervation method," Materials Science Forum
(2011), vol. 675-677 (Pt. 2, Adv. Mat. Science and Technology), p.
1109-1112).
[0008] Although multilayered capsules are generally known in the
art, the quality of these capsules is far from satisfactory. Thus,
there is a need in the industry for microcapsules with improved
barrier and release properties for encapsulated materials such as
perfumes. The present invention satisfies this and other needs of
the industry.
SUMMARY OF THE INVENTION
[0009] The invention relates to a method of making multilayered
microcapsules which comprises providing as a dispersion in an
aqueous vehicle, a hydrophobic internal phase comprising a monomer
and an active agent of a fragrancing or flavouring component such
as a perfume or flavor oil; mixing a first and second
polyelectrolytes in the aqueous vehicle under conditions sufficient
to form a suspension of complex coacervate nodules; depositing the
complex coacervate nodules at an interface of an aqueous vehicle
adjacent the hydrophobic internal phase to form an outer shell of
the microcapsule, wherein the hydrophobic internal phase forms the
core and contains the monomer and fragrancing or flavouring
component therein; and introducing a water soluble reactant into
the aqueous vehicle under conditions sufficient to induce
interfacial polymerization of the monomer inside the outer shell to
form an inner shell at the interface between the internal phase and
the outer shell.
[0010] Advantageously, the outer shell provides a scaffold upon
which the monomer is polymerized, and the inner shell is formed as
a layer that is interlinked with the outer shell, instead of
providing distinct independent layers obtained with processes like
those described heretofore. Also, the first polyelectrolyte may be
positively charged when the pH is less than 8 while the second
polyelectrolyte may be negatively charged when the pH is greater
than 2 such that the outer shell comprises a hydrogel. The first
polyelectrolyte is preferably gelatin while the second
polyelectrolyte is preferably acacia gum. The monomer is preferably
an oil soluble isocyanate, and the reactant is preferably guanazol,
guanidine, or a salt thereof.
[0011] The method optionally further comprises cross-linking the
core-shell capsule chemically or enzymatically before introducing
the reactant into the aqueous vehicle. Also, the pH and temperature
of the aqueous vehicle can be adjusted before, during, or after the
introduction of reactant to control the rate of interfacial
polymerization. The reaction is generally conducted to provide the
inner shell with a volume that is between 10 and 25% and preferably
12 to 20% of the volume of the outer shell. Also, the microcapsules
generally have a size of between 5 .mu.m to 1,000 .mu.m.
[0012] The invention also relates to a multilayered microcapsule
produced by the methods disclosed herein. These multilayer
microcapsules generally comprise an outer shell of a coacervate, an
inner shell of a synthetic polymer, preferably polyurea, and an
internal phase comprising an active agent of a fragrancing or
flavouring component such as a perfume or flavor oil wherein,
advantageously, the outer coacervate shell and the inner polymer
shell form a composite, interlinked structure that does not
delaminate. This novel composite structure is at the origin of the
improved barrier properties of the capsules.
[0013] The invention also relates to the use of the multilayered
microcapsules disclosed herein as a perfuming composition for
consumer products. These consumer products are generally in the
form of a home- or personal-care product that includes the
multilayered microcapsules therein, and are preferably in liquid or
powder form specifically as a detergent composition, a fabric
softener, a hard surface cleaning composition, or a dishwashing
composition, or a shampoo, a hair conditioner, a shower or bath
mousse, oil or gel, a deodorant, or an antiperspirant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram showing a process for making the
multilayered core/shell capsules of the invention.
[0015] FIG. 2 shows a side-by-side comparison between standard
coacervated capsules and the multilayered coacervate/polyurea
core/shell capsules in a surfactant solution.
[0016] FIGS. 3A and B show standard coacervate capsules (A) and the
multilayered (coacervate/polyurea) core/shell capsules (B) in a
shower gel after 24 hrs.
[0017] FIGS. 4A-E show exemplary capsules of the invention having
different sizes and membrane thickness.
[0018] FIG. 5 shows a comparative experiment wherein coacervate
nodules did not deposit at the microcapsule surface and instead
remain dispersed.
[0019] FIG. 6 shows exemplary capsules of the invention having a
corpuscular shell.
[0020] FIG. 7 shows results from an evaluation of capsules of the
invention in a shower gel composition, with the perfume intensity
rated by an untrained panel
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention provides core-shell microcapsules
having dual wall shells of a coacervate and synthetic polymer
composite structure, and preferably of a hydrogel/polyurea
composite structure. Such membrane compositions and particular
structure have been designed and have shown to provide benefits
such as improved bather properties for encapsulated material;
improved adhesive properties; adjustable release properties;
desired mechanical properties; tuned shell density of the capsule;
and, optionally, improved processability and facilitated drying of
the capsules.
[0022] The general concept of the invention is to combine two
processes, namely, the complex coacervation process (for the outer
hydrogel shell) and an interfacial polymerization process (for the
inner polymer shell) in a particular order to obtain
core/multilayer shell capsules having improved properties. The
coacervate constituting the outer shell of the capsule acts as a
scaffold for the polymerization of the inner polymer shell. Such
combination results in the formation of a composite membrane with
two interlinked layers. By composite membrane with two interlinked
layers, it is meant a membrane consisting of layers that are linked
by chemical bonds, thereby forming one inseperable entity. The
structure is therefore such that the outer coacervate is covalently
linked to the inner polymer shell (shown schematically in FIG. 1,
and in the micrographs on FIG. 4). Surprisingly, such composite
membranes with interlinked layers remain interlinked even upon
mechanical breakage, therefore they undergo breakage as a whole
(rather than delaminating or breaking one layer after the other).
Without being bound by theory it is believed that the monomer
present in the internal phase is reacting with the amine
functionalities of the electrolyte (e.g. amine functionality of
protein) even before the water soluble reactant is added to induce
interfacial polymerization. Using mechanical measurements on the
membrane material, described below in the Examples, it was found
here that if multilayered capsules are prepared following the
invention, the polyelectrolyte participates in the interfacial
polymerization, thereby getting intimately integrated into the
membrane. Also, by conducting both the complex coacervation and
interfacial polymerization processes within the same process unit,
the method of the present invention advantageously reduces the
process time and cost while also providing capsules that exhibit
the improved properties defined herein.
[0023] Although the complex coacervation process and the
interfacial polymerization process are each known in the art, it is
believed that these processes have not previously been combined
successfully due to technical difficulties. It is not possible to
simply associate these two different processes to build
microcapsules with two (or more) distinct walls. One possible way
may be for the skilled person to start by creating a standard
aqueous suspension of synthetic microcapsules made by interfacial
polymerization and then deposit on the surface of the primary
microcapsule, a hydrogel following the process of complex
coacervation. This type of approach is disclosed in British patent
application GB 1141186 but is unsuitable because the polymer phase
separation (i.e., complex coacervation) occurs in a range of pH
which is "non-conventional" for the polymerization process.
Therefore, the simple addition of the state of the art of two
processes one after the other will not work. In fact, comparative
experiments were performed following the approach disclosed in GB
1141186. The objective was to form a membrane of coacervate onto
polyurea microcapsules. This process proved unsuccessful, as the
coacervate nodules did not deposit at the microcapsule surface and
stayed in the continuous aqueous media, and this is shown in FIG. 5
wherein the two separate populations of particles (coacervate
nodule and polyurea microcapsules) can be seen.
[0024] In contrast, the present invention induces a specific
modification of the membrane of the primary microcapsule that is
initially made by complex coacervation in order to obtain
coacervated microcapsules exhibiting high barrier properties (i.e.,
low permeability). Typically, the specific membrane modification is
carried out by inducing polymerization within the coacervate, which
is typically a hydrogel. This local reinforcement is only permitted
if the polymerization starts from inside of the microcapsule, so
that the primary microcapsule is provided with a monomer within its
core. This is achieved by adding a monomer that is unreactive with
the other components that are present in the coacervation process,
and then by polymerizing the monomer in the capsules after the
capsules are formed. The compatibility of the two processes is not
an issue as in the prior art.
[0025] A typical process for making the microcapsule of the present
invention comprises the following steps:
I. Formation of the First, Outer Hydrogel Shell by Complex
Coacervation
[0026] Two oppositely charged polyelectrolytes are mixed under
specific temperature, pH and concentration conditions to induce
polymer phase separation, so as to produce a suspension of complex
coacervate nodules. The complex coacervate nodules have to deposit
at the active interface to form core-shell capsules. Optionally,
the capsules undergo a chemical or enzymatic cross-linking step.
Furthermore, the active agent to be encapsulated, typically a
fragrancing material such as a perfume oil, must already contain
the appropriate monomer (e.g., an isocyanate) which is later
polymerized to form the inner shell.
II. Formation of the Second, Inner Shell by Polymerization at the
Coacervate/Oil Interface
[0027] The polymerization of the monomer contained within the core
of the capsule is induced by introducing a water soluble reactant
in the continuous phase. The coacervate or hydrogel shell is needed
to provide a scaffold upon which the synthetic polymer may be
polymerized. The reactant is dependent of the nature of the
monomer. In a preferred embodiment the polymerization reaction is
induced between an isocyanate and an amine (or diamine) to obtain a
polyurea polymer. This is generally achieved by first adjusting the
pH and then introducing, preferably drop wise or in portions, a
solution of an amine (or diamine) into the capsule dispersion. The
polymerization is then induced at the hydrogel/oil interface,
thereby forming the second, inner, polyurea shell. The monomer
contained within the core of the capsule and the reactant
introduced in the aqueous continuous phase wherein the capsules are
dispersed, are both needed to induce the polymerization and finally
the formation of the inner shell (e.g., polyurea). Preferably, the
reactant is introduced slowly. Typically, the pH and the
temperature of the capsule suspension are tuned, before, during, or
after the introduction of reactant, to control the polymerization
time.
[0028] In the microcapsules of the invention, the hydrogel shell
(coacervate) improves the adhesion and the mechanical properties of
the capsule while the inner shell (polyurea) provides additional
and superior barrier properties to obtain a microcapsules that
exhibits excellent resistance against evaporation of the active
agent when the capsules are in the dry state as well as excellent
resistance against destabilization of the capsules in harsh
environments, e.g., in detergent or surfactant solutions.
[0029] Typically, the microcapsules of the invention are made from
the following preferred ingredients: [0030] (1) A first
polyelectrolyte (Polyelectrolyte I) of one charge, preferably
selected among proteins that are able to interact with an
electrolyte or polyelectrolyte that has an opposite charge to thus
form a coacervate phase having the ability to coat hydrophobic
interfaces in order to form the capsules. In a preferred
embodiment, Polyelectrolyte I is positively charged for pH<8 so
as to form gels or highly viscous solutions in water below the
gelling temperature, and lower viscosity solutions in water at a
temperature above the melting point of the gel. The viscosity above
the gelling temperature is typically lower than 0.1 Pas; below the
gelling temperature, the elastic modulus G' of the gel is typically
in the range 0.1-15 kPa when measured during the first 24 hours
after gel formation, using the measurement methods based on shear
rheometry (such methods, along with the definitions relevant for
the gelling temperature, are described, for example, in Parker, A.
and Normand, V., Soft Matter, 6, pp 4916-4919 (2010). During the
coacervation process, the temperature of oil introduction may be
adjusted to a value sufficient to shorten the membrane formation
step and avoid premature reaction of the isocyanate at the
oil/water interface. Preferably, Polyelectrolyte I is a gelatin
material. [0031] (2) A second polyelectrolyte (Polyelectrolyte II),
which is preferably selected among polysaccharides or another
polymer bearing charges of opposite polarity compared to
Polyelectrolyte I. Generally, Polyelectrolyte II is negatively
charged for pH>2. Preferably, Polyelectrolyte II is a
polyelectrolyte that is only weakly negatively charged at pH>2;
such polyelectrolytes are, for example, carboxymethyl cellulose,
sodium carboxymethyl guar gum, or xanthan gum, or yet plant gums
such as acacia gum. Most preferably, it is acacia gum (gum arabic).
The ratio between polyelectrolyte 1 and polyelectrolyte 2 is
preferably comprised between 10/0.1 to 0.1/10. [0032] (3) A monomer
which is typically soluble in oil and able to interact and
polymerize with a water soluble reactant. Preferably, the monomer
is an isocyanate. [0033] (4) A reactant for the monomer, which
reactant is soluble in water and is generally selected from water
soluble compounds selected from the group consisting of diamines,
polyols, alcohols and other reactants that are able to induce the
polymerization of the monomer that is contained in the core of the
capsule. Preferred reactants include guanazol or guanidine. [0034]
(5) An active agent which is encapsulated within the microcapsules.
By "active agent" what is meant is a volatile material that would
be rapidly released. Any type of volatile material can be used,
including flavors and fragrances, but the present microcapsules are
ideally suitable for encapsulating fragrancing components such as
perfume oils.
[0035] The terms "flavors" and "fragrances" as used herein are
deemed to define a variety of flavour and fragrance materials of
both natural and synthetic origin. They include single compounds or
mixtures. Specific examples of such components may be found in the
literature, e.g. in Fenarsoli's handbook of Flavor Ingredients,
1975, CRC Press; synthetic Food Adjuncts, 1947 by M. B. Jacobs,
edited by van Nostrand; or Perfume and Flavor Chemicals by S.
Arctander 1969, Montclair, N.J. (USA), or any more recent versions
of such textbooks. These substances are well known to the person
skilled in the art of perfuming, flavoring and/or aromatising
consumer products, i.e. of imparting an odour and/or flavour or
taste to a consumer product traditionally perfumed or flavoured, or
of modifying the odour and/or taste of the consumer product.
[0036] Accordingly, in an embodiment, the ingredient comprises at
least 5 wt. % , preferably at least 10 wt. %, preferably at least
20 wt. %, more preferably at least 30 wt. % and most preferably at
least 40 wt. % of chemical compounds having a vapour pressure of
.gtoreq.0.007 Pa at 25.degree. C.
[0037] Preferably, at least 10 wt. % have a vapour pressure of
.gtoreq.0.1, more preferably, at least 10 wt. % have a vapour
pressure of .gtoreq.1 Pa at 25.degree. C., and most preferably, at
least 10 wt. % have a vapour pressure of .gtoreq.10 Pa at
25.degree. C. The value of 0.007 Pa at 25.degree. C. is selected
because it encompasses most of the compounds used by the skilled
flavourist and/or perfumer. Compounds meeting these criteria are
generally regarded as having a volatile character. In addition,
compounds that remain odourless due to a lower volatility are
excluded. The limit of 1 wt. % of such compounds is regarded to
constitute a substantial part of the ingredient. The method of the
present invention, however, allows for efficient encapsulation of
more volatile ingredients being present in higher amounts of the
total ingredients.
[0038] For the purpose of the present invention and for the sake of
convenience, the vapour pressure is determined by calculation.
Accordingly, the method disclosed in "EPI suite"; 2000 U.S.
Environmental Protection Agency, is used to determine the concrete
value of the vapour pressure of a specific compound or component of
the ingredient. This software is freely available and is based on
average values of vapour pressures obtained by various methods of
different scientists.
[0039] The fragrance compound limonene is adduced for illustrating
the determination of vapour pressure by calculation: by applying
the method "EPI suite", limonene is calculated to have a vapour
pressure of about 193 Pa at 25.degree. C.
[0040] The monomer that is used in the process of the invention
preferably has at least two isocyanate groups, and more preferably,
at least three isocyanate groups. With these functional groups, an
optimal reticulation or network of the capsule wall is achieved,
providing thus microcapsules exhibiting a surprisingly useful dual
shell barrier that provides a prolonged slow release of fragrance,
as well as a surprisingly improved stability of the microcapsules
in a wide range of consumer products. Low volatility aliphatic
polyisocyanate products are especially preferred because of their
low toxicity. Such products are characterized by a low
concentration of monomeric hexamethylene diisocanate (HDI);
typically, such products contain at most 0.7% HDI and are available
commercially. In particular, the isocyanate monomer is preferably
hexamethylene diisocyanate or isophorone diisocyanate.
[0041] In the process of the invention, the reactant is preferably
selected from the group of water soluble guanidine salts and
guanidine. By "water soluble guanidine salt," it is meant a salt
soluble in water and resulting from the reaction of guanidine with
an acid. One example of such salts is guanidine carbonate. The
polyurea wall of the microcapsules is the result of the interfacial
polymerization between the monomer in the internal phase and the
reactant. Preferably, for each mole of isocyanate monomer contained
in the internal phase, 1 to 3 moles, and preferably 1.2 to 2 moles,
of guanidine or guanidine salt are added for the interfacial
polymerization. Accordingly, an excess of the reactant is provided
to assure complete polymerization of the monomer. No specific
action is required to induce the polymerization between the
isocyanate monomer and the guanidine or guanidine salt in the
dispersion. The reaction starts immediately after adding the
reactant. Preferably, the reactant is added slowly with the
reaction maintained for 2 to 15 hours, and preferably for 4 to 10
hours. The specific composition of the polyurea wall is key in
obtaining dual wall microcapsules that include a fine balance
between release and retention so as to achieve satisfactory slow
and constant release of the encapsulated fragrance component over
time, such as when the capsules are eventually placed on textiles
or hair, while also exhibiting the desired stability in the product
base (e.g., counteracting efficiently the extraction of the perfume
by the surfactants contained in the consumer product). The
combination of isocyanate and guanidine or guanidine salts enable
this fine tuning of the properties and stability of the capsules.
Of course, skilled artisans can select other combinations of
monomers and reactants to achieve the desired results for any
particular microcapsules for fragrancing of a specific consumer
product.
[0042] The multilayered microcapsule of the present invention is a
core/multilayershell system comprising a membrane which typically
contains gelatin, gum arabic and water; and an internal phase which
typically contains a monomer (e.g., the isocyanate) and the active
agent (e.g., a fragrancing component such as a perfume oil). The
relative proportion of each constituent within the microcapsule of
the invention varies, depending on the mean diameter and the
thickness of the membrane that is to be formed. Table I below shows
exemplary microcapsules of the invention having different sizes and
membrane thickness. The morphologies of five types of microcapsules
(Samples #1 to #5) are shown in FIGS. 4A-E. The volume fraction of
the membrane represents less than 15% for a "large" microcapsule
having a thin membrane (e.g., Sample #1, FIG. 4A) and reaches up to
80% for a "small" capsule having a thick membrane (e.g., Sample #5,
FIG. 4E).
TABLE-US-00001 TABLE I Multilayered Microcapsules having different
sizes and membrane thickness. Numbers # refer to image in FIG. 4
Volume fraction Outer inner shell:total shell Core shell Type 1
Type 2 radius thickness (polyurea thin) (polyurea thick) # (.mu.m)
(.mu.m) % v/v % v/v Thick outer 5 10 7 0.13 1.01 shell 10 15 0.03
0.27 50 50 0.07 0.57 100 100 0.07 0.57 3 145 68 0.23 1.81 2 300 45
0.95 7.13 400 100 0.52 4.03 600 100 0.84 6.37 800 100 1.17 8.62
1000 100 1.49 10.78 1500 100 2.29 15.77 Thin outer 10 2 0.68 5.21
shell 4 37 6 0.87 6.56 50 2 3.85 24.26 100 2 7.55 39.52 200 2 14.16
56.90 1 365 20 2.80 18.73 600 10 8.95 44.03 800 10 11.64 51.30 1000
10 14.16 56.90 1500 10 19.89 66.52
[0043] Typically, the microcapsules of the invention have a mean
core radius size of between 5 .mu.m and 1,000 .mu..mu.m.
Microcapsules having a mean core radius size between 100 .mu.m and
500 .mu.m have proved useful in certain body care products. In
other cases, microcapsules wherein the mean core radius size was
between 10 and 40 .mu.m also proved to be useful. The size of the
microcapsules can be easily adjusted by the skilled person as a
function of the nature of the desired application
[0044] The volume of the inner shell typically represents 0.1 to
80% of the total volume of the shell.
[0045] The final composite membrane properties depend on multiple
factors such as the monomer concentration within the capsule core.
The initial thickness of the capsule membrane also affects the
final composite membrane properties. The concentration of the
monomer is adjusted to ensure that the concentration of the free
monomer in the final product is below safety requirement.
[0046] The perfume oil in the internal phase of the microcapsules
of the invention may comprise a single compound or a mixture of
compounds. Non-limiting examples of active perfuming ingredients
susceptible of being advantageously encapsulated according to the
invention are as follows: [0047] 2,6,10-Trimethyl-9-undecenal
[0048] 2-Propenyl hexanoate [0049] cis-3-Hexenyl 2-methylbutanoate
[0050] Decanal [0051] cis-3 -Hexenyl-methyl-carbonate [0052]
Nonanal [0053] 9-Decen-1-o1 [0054] Methyl-3-heptanone oxime [0055]
(2S,5R)-2-Isopropyl-5-methylcyclohexanone [0056]
1,7,7-Trimethylbicyclo[2.2.1]heptan-2-one [0057] para
tert-Butylcyclohexanone [0058] Isobornyl acetate [0059] Cyclohexyl
2-hydroxybenzoate [0060] Allyl cyclohexyl propionate [0061]
Dihydroterpenyl acetate [0062]
2,4,6-Trimethyl-4-phenyl-meta-dioxane [0063]
2-Heptyl-1-cyclopentanone [0064] (3,4-Dihydroxyphenyl)acetate
[0065] Trimethyl cyclodecatrine epoxide [0066] 6
Ethyl-3,10,10-trimethyl-4-oxaspiro[4.5]deca-1,6-diene [0067]
4-tert-Butyl-cyclohexyl acetate [0068] 1-(1-Ethoxyethoxy)propane
[0069] Allyl (2-methylbutoxy)acetate [0070]
Prop-2-enyl2-(3-methylbutoxy)acetate [0071] 1-Octen-3-ol [0072]
trans-Anethole [0073] 3-(4-tert-Butylphenyl)propanal [0074]
2,6-Nonadien-1-ol [0075] [(3,7-Dimethyl-6-octenyl)oxy]-acetaldehyde
[0076] Lauronitrile [0077]
2,4-Dimethyl-3-cyclohexene-1-carbaldehyde [0078]
1-(2,6,6-Trimethyl-1,3-cyclohexadien-1-yl)-2-buten-1-one [0079]
1-(2,6,6-Trimethyl-2-cydohexen-1-yl)-, (E)-2-buten-1-one [0080]
gamma-Decalactone [0081] trans-4-Decenal [0082] 2-Pentyl
cyclopentanone [0083] 1-(2,6,6 Trimethyl-3
-Cyclohexen-1-yl)-2-Buten-1-one) [0084] 1,1'-oxybis-Benzene [0085]
1-(5,5-Dimethyl-1-cyclohexen-1-yl-4-enten-1-one [0086]
Ethyl-2-methylbutanoate [0087]
1,3,3-Trimethyl-2-oxabicyclo[2.2.2]octane [0088] Eugenol [0089]
3-(3-Isopropylphenyl)butanal [0090] Methyl2-octynoate [0091]
4-(2,6,6-Trimethyl-1-cyclohexen-1-yl-3 -buten-2-one [0092]
2-Methoxy-3-(2-methylpropyl)-pyrazine [0093] Isobutyl quinoline
[0094] Isoeugenol [0095]
Tetrahydro-6-(3-pentenyl)-2H-Pyran-2-one
[0096] The microcapsules of the present invention have multiple
uses. For example, the microcapsules of the invention can be
included in perfumery applications where capsules made by
coacervation or by interfacial polymerization can be used,
including but not limited to, consumer products such as, body wash,
body care, air care and fine fragrances. In one embodiment,
capsules with strong adhesive properties, are preferred. Whereas
strong adhesive properties have been described for certain
polyelectrolyte complexes found in nature, it has until now been
impossible to achieve coacervate-based adhesion mechanisms for
microcapsules while also retaining the outstanding, low
permeability, barrier properties provided by synthetic polyurea
shells. Surprisingly, the presence of the coacervate component of
the shell formed by the protein and the weakly anionic
polyelectrolyte provides outstanding adhesive properties to the
capsules of this invention.
[0097] The microcapsules of the invention described herein can be
used as perfuming ingredients in consumer products of the home- or
personal-care type. This result is highly surprising since the
consumer products contain high amounts (typically more than 10% of
their own weight) of specific type of
surfactant/tensioactive/solvents which are known to significantly
diminish the stability and the performance of other similar prior
art capsules. The use of the microcapsules disclosed herein
provides improved deposition of the perfume on the treated surface
together with an improved stability in a chemically aggressive
environment. In other words, the use of the capsules in various
applications provides unforeseeable advantages over the same use of
other similar prior art capsules.
[0098] The present invention also relates to the use of such
microcapsules in a consumer product that is in the form of a home-
or personal-care product. Such products may be either a solid or a
liquid product. According to a particular embodiment, liquid
products are preferred. The expression "home- or personal-care" has
here the usual meaning in the art, and in particular, it includes
products such as body-care, hair-care or home-care products.
Examples of liquid products according to the invention may be
selected from the group consisting of a shampoo or a hair
conditioner, a liquid detergent, a fabric softener, a shower or
bath mousse, oil or gel, a deodorant or an antiperspirant.
Preferably, the liquid perfumed product is a shower gel, shampoo, a
liquid detergent or a fabric softener. Examples of solid products
according to the invention may be selected from the group
consisting of a soap bar, a powder detergent or an air-freshener.
As detergent products, there are considered applications such as
detergent compositions or cleaning products for washing up or for
cleaning various surfaces, for example, intended for textiles,
dishes or hard surfaces (floors, tiles, stone-floors, etc).
Preferably, the surface is a textile.
[0099] Conveniently, the microcapsules of the invention may be used
as such to perfume the consumer products. For example, the
microcapsules may be directly added to a consumer product in an
amount of 0.1-30 wt. %, e.g. resulting in a total perfume content
of about 0.0333-10 wt. %. Preferably, a consumer product according
to the invention comprises about 0.01 to 4 wt. %, or even 4.5%, of
its own weight, in capsules as defined above and containing the
perfume oil ingredients. Of course, the above concentration may be
adapted according to the olfactive effect desired in each
product.
[0100] The invention also provides consumer products such as a
laundry and cleaning composition comprising microcapsules of the
invention and a detersive ingredient. Preferably, the laundry and
cleaning composition is selected from the group consisting of a
detergent composition, a hard surface cleaning composition, and a
dishwashing composition. The invention also provides a process for
making such laundry and cleaning composition, which comprises the
step of combining the microcapsules of the invention, by means
selected from spraying, dry-mixing, and mixtures thereof, with the
detersive ingredient.
[0101] Most preferably, the laundry and cleaning composition is a
fabric detergent or softener composition. Typical examples of
fabric detergent or softener composition into which the
microcapsules of the invention can be incorporated are described in
WO 97/34986 or in U.S. Pat. Nos. 4,137,180 and 5,236,615 or EP 799
885. Other typical detergent and softening compositions which can
be used are described in works such as Ullman's Encyclopedia of
Industrial Chemistry, vol. A8, pages 315-448 (1987) and vol. A25,
pages 747-817 (1994); Flick, Advanced Cleaning Product
Formulations, Noye Publication, Park Ridge, N.J. (1989); Showell,
in Surfactant Science Series, vol. 71: Powdered Detergents, Marcel
Dekker, New York (1988); Proceedings of the World Conference on
Detergents (4th, 1998, Montreux, Switzerland), AOCS print.
[0102] Another advantage of the invention is that the microcapsules
as disclosed herein results in beneficial effects on the retention
of the perfume oil ingredients in the microcapsules over time.
Thus, the aging process of the microcapsules is reduced, such that
the microcapsules or products containing them can be stored over
time for longer periods compared to other formulations of
microcapsules that are not prepared as noted herein. Thus, the
present invention increases the shelf life of home- or
personal-care products that contains these microcapsules.
[0103] Depending on the safety status of the final product, the
microcapsule of the invention may also be used in food applications
where capsules made by coacervation are commonly used.
EXAMPLES
[0104] The following non-limiting examples are illustrative of the
present invention.
Example 1
[0105] Multilayered Polyurea/Coacervate Capsules Cross-Linked with
Glutaraldehyde
[0106] Aqueous solutions of (A) 10% wt. pork gelatine (250 Bloom,
supplied by Norland); (B) 10% wt. gum arabic (EFFICACIA.RTM., from
CNI); and (C) 3% wt. guanazol are prepared separately. The
fragrance component to be encapsulated is mixed with (D) 8% of
isocyanate (Desmodur.RTM. N4; origin: Bayer Material Science).
[0107] In a vessel at 40.degree. C., 25.4 g of solution (A) and
12.7 g of solution (B) are added to 92.8 g of warm demineralised
water under mechanical shear. The pH is adjusted to 4.5 using HCl
1M. The mixture is maintained at 40.degree. C. for 15 min and then
cooled down to 35-31.degree. C. at a rate of 0.5.degree. C.
min.sup.-1.
[0108] 19.1 g of solution (D) is slowly added to the mixture and
homogenised at 350 RPM for a period of 5 min, so as to reach an
average droplet size of 300 .mu.m. Mechanical shear is maintained
while the solution is let to cool down at 10.degree. C. at a rate
of 0.5.degree. C. min.sup.-1. The stirring speed is then slightly
decreased, and 0.102 g of glutaraldehyde (aq.50% wt. Supplied by
Sigma-Aldrich) is added to the mixture. Cross-linking is allowed to
proceed for 4 to 10 hours at 20.degree. C.
[0109] 20 g of solution (C) is then added to the aqueous suspension
of microcapsules at a rate of 1 ml/min. The mixture is kept under
agitation for 1 to 4 hours at room temperature or optionally heated
to temperature between 40-70.degree. C.
[0110] The result is an aqueous suspension of multilayered capsules
with composite polyurea/coacervate shells, the coacervate component
being formed by gelatin and gum arabic.
[0111] These capsules were inspected visually using microscopy.
Rupturing the capsules (for example, by exerting mechanical force
onto the capsules with mortar and pestle or by squeezing them
between two glass slides) and subsequent observation in the
microscope indicates that even upon fracture of the entire capsule,
the individual layers of the formed multilayer shells remain
interlinked. No delamination of the coacervate from the polyurea is
observed, indicating that indeed the multilayer capsule shells
formed are a composite, interlinked material.
Example 2
[0112] Multilayered Polyurea/Coacervate Capsules Cross-Linked
Enzymatically with Transglutaminase
[0113] Solution (A') is an aqueous solution of 10% wt. Warm water
fish gelatine (230 Bloom, supplied by Wheishardt).
[0114] In a vessel at 40.degree. C., 25.4 g of solution (A') and
12.7 g of solution (B) (see Example 1) are added to 92.8 g of warm
demineralised water under mechanical shear. The pH is adjusted to
4.5 using HCl 1M. The mixture is maintained at 40.degree. C. for 15
min and then cooled down to 35-31.degree. C. at a rate of
0.5.degree. C. min.sup.-1.
[0115] 19.1 g of solution (D) (see Example 1) is slowly added to
the mixture and homogenised at 350 RPM during 5 min, so as to reach
an average droplet size of 300 .mu.m. Mechanical shear is
maintained while the solution is let to cool down at 10.degree. C.
at a rate of 0.5.degree. C. min.sup.-1. The stirring speed is
slightly decreased, the pH is adjusted to 4.5 and 1.01 g of
transglutaminase (ACTIVA.RTM. WM supplied by Ajinomoto) is added to
the mixture. Cross-linking is allowed to proceed for 4 to 10 hours
at 20.degree. C.
[0116] 20 g of solution (C) (see Example 1) is then added to the
aqueous suspension of microcapsules at a rate of 1 ml/min The
mixture is kept under agitation for 1 to 4 hours at room
temperature or optionally heated to temperature between
40-70.degree. C.
Example 3
Multilayered Polyurea/Coacervate Capsules Prepared by Initial
In-Situ Polymerization Within a Coacervate Shell Followed by
Cross-Linking
[0117] In a vessel at 40.degree. C., 25.4 g of solution (A') and
12.7 g of solution (B) (see Example 1) are added to 92.8 g of warm
demineralised water under mechanical shear. The pH is adjusted to
4.5 using HCl 1M. The mixture is maintained at 40.degree. C. for 15
min and then cooled down to 35-31.degree. C. at a rate of
0.5.degree. C. min.sup.-1.
[0118] 19.1 g of solution (D) (see Example 1) is slowly added to
the mixture and homogenised at 350 RPM for 5 min, so as to reach an
average droplet size of 300 .mu.m. Mechanical shear is maintained
while the solution is let to cool down at 10.degree. C. at a rate
of 0.5.degree. C. min.sup.-1 and maintained at 10.degree. C. for 1
hour. The aqueous suspension of microcapsules is then warmed up to
room temperature and 20 g of solution (C) (see Example 1) is then
added to the aqueous suspension of microcapsules at a rate of 1
ml/min The mixture is kept under agitation for 1 to 4 hours at room
temperature.
[0119] Finally, 0.102 g of glutaraldehyde (aq. 50% wt. Supplied by
Sigma-Aldrich) is added to the mixture and cross-linking is allowed
to proceed for 4 to 10 hours at 20.degree. C.
Example 4
[0120] Multilayered Polyurea/Coacervate Capsules (Thin Shell)
Cross-Linked with Glutaraldehyde
[0121] In a vessel at 40.degree. C., 19.1 g of solution (A) (see
Example 1) and 19.1 g of solution (B) (see Example 1) are added to
92.8 g of warm demineralised water under mechanical shear. The pH
is adjusted to 4.4 using HCl 1M. The mixture is maintained at
40.degree. C. for 15 min and then cooled down to 35-31.degree. C.
at a rate of 0.5.degree. C. min.sup.-1.
[0122] 19.1 g of solution (D) (see Example 1) is slowly added to
the mixture and homogenised at 350 RPM for 5 min, so as to reach an
average droplet size of 300 .mu.m. Mechanical shear is maintained
while the solution is let to cool down at 10.degree. C. at a rate
of 0.5.degree. C. min.sup.-1. The stirring speed is slightly
decreased, and 0.102 g of glutaraldehyde (aq.50% wt. Supplied by
Sigma-Aldrich) is added to the mixture. Cross-linking is allowed to
proceed for 4 to 10 hours at 20.degree. C.
[0123] 20 g of solution (C) (see Example 1) is then added to the
aqueous suspension of microcapsules at a rate of 1 ml/min The
mixture is kept under agitation for 1 to 4 hours at room
temperature or optionally heated to temperature between
40-70.degree. C.
Example 5
[0124] Multilayered Polyurea/Coacervate Capsules (Corpuscular
Shell) Cross-Linked with Glutaraldehyde
[0125] In a vessel at 40.degree. C., 12.7 g of solution (A) (see
Example 1) and 25.4 g of solution (B) (see Example 1) are added to
92.8 g of warm demineralised water under mechanical shear. The pH
is adjusted to 4.0 using HCl 1M. The mixture is maintained at
40.degree. C. for 15 min and then cooled down to 35-31.degree. C.
at a rate between 1.5 and 0.5.degree. C. min.sup.-1.
[0126] 19.1 g of solution (D) (see Example 1) is slowly added to
the mixture and homogenised at 350 RPM for 5 min, so as to reach an
average droplet size of 300 .mu.m. Mechanical shear is maintained
while the solution is let to cool down at 10.degree. C. at a rate
of 0.5.degree. C. min.sup.-1. The stirring speed is slightly
decreased, and 0.102 g of glutaraldehyde (aq.50% wt. Supplied by
Sigma-Aldrich) is added to the mixture. Cross-linking is allowed to
proceed for 4 to 10 hours at 20.degree. C.
[0127] 20 g of solution (C) (see Example 1) is then added to the
aqueous suspension of microcapsules at a rate of 1 ml/min The
mixture is kept under agitation for 1 to 4 hours at room
temperature or optionally heated to temperature between
40-70.degree. C.
[0128] The resulting capsules exhibit a corpuscular shell as shown
FIG. 6
Example 6
Improved Stability in Surfactant Solution
[0129] The stability of standard coacervated capsules, prepared in
a manner similar to that described by Meyer A., Perfume
microencapsulation by complex coacervation, Chimia 46 (1992)
101-102, and hydrogel/polyurea capsules of the invention, in
surfactant solution, were compared. As shown in FIG. 2, the
hydrogel/polyurea capsules prepared as described in Example 1 were
found to be significantly more stable than the standard coacervated
capsules. In particular, after 15 hours in SDS, the shells of the
standard coacervated capsules were completely destroyed, thus
releasing the encapsulated material. In contrast, the shells of the
hydrogel /polyurea capsules of the invention remained intact after
15 hours in SDS, thus preventing the premature release of the
encapsulated material. This result shows that the presence of the
inner synthetic polymer (polyurea) within the hydrogel shell
significantly improves the stability of the capsules, even when
applied in aggressive, highly concentrated surfactant media.
Example 7
Improved Stability in a Shower Gel Application
[0130] The stability of standard coacervated capsules, prepared in
a manner similar to that described by Meyer A., Perfume
microencapsulation by complex coacervation, Chimia 46 (1992)
101-102.) and the hydrogel/polyurea capsules of the invention were
compared in a shower gel. The model shower gel base used was
composed of 50% deionized water, 5% thickener
(acrylates/beheneth-25 methacrylate copolymer, available from
Lubrizol), 43% surfactants (sodium pareth sulfate and
cocamidopropyl betaine), 0.5% preservative (sodium benzoate);
sodium hydroxide and citric acid are used to adjust the pH
value.
[0131] The standard capsules contained the same active agent as in
the internal phase of the hydrogel /polyurea capsules. As shown in
FIGS. 3A and B, the hydrogel/polyurea capsules prepared as
described in Example 1 are significantly more stable than the
standard coacervated capsules. In particular, after 24 hours in the
shower gel, standard coacervated capsules have a 65% leakage while
no leakage is found in the hydrogel/polyurea capsules of the
invention, thus preventing the premature release of the
encapsulated material. This result further demonstrates that the
presence of the inner synthetic polymer (polyurea) within the
hydrogel shell significantly improves the stability of the capsules
when subjected to highly concentrated surfactant media.
Example 8
Evaluation of Capsule Performance in a Model Shower Gel
Composition: `Blooming` Effect Upon Lathering
[0132] Multilayered capsules were prepared as described in Example
1. The release properties of the capsules were evaluated in a model
shower gel base (see composition in Example 7) in panel tests with
twelve untrained participants. The perfume was a model perfume
composition with predominantly citrus and fruity notes. The
panelists were asked to rate the perceived perfume intensity of the
shower gel before usage (5 ml of shower gel held in the palm of the
panelist's hands) and after lathering for ten seconds with warm
water. The panelists were asked to rate the `before` and `after`
samples on a scale of 0 to 4 (0: no perfume perceived, 1: weak; 2:
medium; 3: strong; 4: very strong). This test was performed on
three different samples, each tested individually but by the same
group of panelists. Sample A: shower gel containing 1.2% w/w free
perfume; Sample B: shower gel containing 1.2% w/w encapsulated
perfume according to example 5; Sample C: shower gel containing 1%
w/w encapsulated perfume according to example 5 and 0.2% w/w free
perfume. Key results of the panel test are summarized in FIG. 7;
shown are the mean values of the panelists' intensity ratings along
with the standard deviation. Only a minor increase in perceived
intensity upon lathering was observed for the free perfume (Sample
A). In contrast, if the perfume was present in encapsulated form, a
significant and very strong difference was perceived by all of the
panelists, with mean intensity values increasing from 1.1 to 3.1
upon lathering. The effect was still very strong even if a smaller
amount of capsules was added in combination with a small amount of
free oil.
Example 9
Use of the Perfume Capsules to Provide Sequential Delivery of Two
Perfumes in a Model Shower Gel Composition Upon Lathering
[0133] This example demonstrated the capacity of the capsules to
provide sequential delivery properties in a consumer product such
as a cosmetic cream or lotion, shower gel, or a liquid
soap/handwash. The objective was to first deliver a perfume
(perfume 1) added to the base as a liquid (without being
encapsulated encapsulation), and to add another perfume (perfume 2)
in encapsulated form. Upon application of the product, the
panelists should perceive predominantly perfume 1 when smelling the
neat shower gel before lathering, but not perfume 2. Then, upon
lathering, perfume 2 should be released when the capsules are
broken due to mechanical rubbing. Multilayered capsules were
prepared as described in Example 1. The release properties of the
capsules were evaluated in a model shower gel composition in panel
tests with twelve untrained participants. Here, perfume 1 was of a
floral note (`muguet` type) and perfume 2 was a composition with
predominantly citrus and fruity notes. As in example 8, the
panelists were asked to rate the perceived perfume tonality of the
shower gel before usage (5 ml of shower gel held in the palm of the
panelist's hands) and after lathering for ten seconds with warm
water.
[0134] The sample to be evaluated is a shower gel base (see
composition in example 7) containing 1.0% w/w encapsulated perfume
2 according to example 5 and 0.2% w/w free perfume 1 The panelists
were asked to describe the `before` and `after` samples by choosing
from a provided list of descriptors ("floral", "green", "fresh",
"fruity", "citrus", "watery") but were also asked to provide any
additional descriptors of their choice. Furthermore, the panelists
were asked generally if they perceived a change in tonality upon
lathering ("yes", "no" or "not sure" question), and if they
perceived a overall increase in intensity upon lathering ("yes",
"no" or "not sure" question). The ratings were then collected and
summarized. Before lathering, the top counts descriptors were
"floral" (by 83% of the panelists), "green" (by 42% of the
panelists), or "soap-like" (by 16% of the panelists). After
lathering, the top descriptors were "citrus" (by 83% of the
panelists), "fruity" (by 54% of the panelists), "fresh" (by 25% of
the panelists); additional free descriptors mentioned spontaneously
by the panelists were "grapefruit" and "passion fruit". After
lathering, 100% of the panelists perceived an overall increase in
perfume intensity. 83% of the panelists perceived a clear and
unambiguous change on tonality upon lathering, whereas 17% of the
panelists were not sure.
Example 10
Characterization of the Mechanical Properties of the Composite,
Interlinked Shell Material
[0135] To characterize the composite, interlinked layer of the
shell material, mechanical tests were performed using the method of
interfacial rheology. Such experiments allow for precise
measurement of the elastic shear modulus of the interfacial film.
The theory and details of interfacial rheology measurements are
described in detail in the scientific literature (for example:
"Interfacial transport processes and rheology" by D. A. Edwards, H.
Brenner and D. T. Wasan, Butterworth-Heinemann, Boston Mass., USA,
1991). Interfacial polymerization leads to a strong increase of the
elastic shear modulus of the interface, G'i (measured in units of
Newtons per meter). In contrast, if no polymerization occurs, the
elastic shear modulus of the interface is undetectable. Equipment
for interfacial rheology measurements is available from a variety
of instrument manufacturers (such as Anton Paar, Germany; TA
Instruments, USA; or KSV Instruments, Finland). For
characterization of the interfacial films described here, an Anton
Paar MCR300 instrument is used, and the measuring setup used is a
biconical disk geometry, following the methods described in detail
in the literature (P. Erni et al., Review of Scientific
Instruments, Vol. 74, pp 4916-4924).
[0136] Interfacial rheology measurements were performed for three
different situations to elucidate the interlinked nature of the
shell material. In all cases, the temperature was 45.degree. C.
[0137] 1. A control experiment was performed by measuring the
elastic shear modulus of the interface between amine-free and
polyelectrolyte-free (in particular, gelatin-free) water adjusted
to three different pH values (pH 2, pH 7, and pH 11) on one side,
and the fragrance oil containing 8% of the oil-soluble isocyanate
monomer on the other side. This control experiment was performed to
confirm that the isocyanate did not polymerize with any components
(for example: nitrogen-containing impurities) in the absence of
amines and in the absence of gelatin. The result was that in the
absence of amines and in the absence of gelatin in the water phase,
the elastic shear modulus of the interface was always zero, G'i=0,
indicating that indeed no polymerization occurs.
[0138] 2. A second control experiment was performed to measure the
elastic shear modulus of the interface G'i for single layer,
polymer-only shell materials. In this experiment, the water phase
was an aqueous amine solution (3% guanazol in deionized water) at
pH 11 and the oil phase was again the fragrance component
containing 8% isocyanate. As expected, significant polymerization
occurred and values for G'i could already be detected after two
minutes of polymerization. The interfacial modulus increased over
the course of an hour and attained a value of 0.7 N/m after 190
minutes, and then remained constant.
[0139] 3. A third control experiment was performed to verify that
the polyelectrolyte (gelatin) alone did not form an elastic
interfacial film at the temperature studied (45.degree. C., which
is above the melting temperature of the gelatin). A solution of
gelatin (type A, 275 Bloom) at 0.5% at pH 4.5 was prepared, and
brought into contact with the monomer-free fragrance oil. The
elastic shear modulus of the interface remained at zero during 36
hours, G'i=0, indicating that gelatin does not form an elastic firm
at this temperature. Furthermore, it was also verified seperately
that the gelatin did form a bulk gel but remained in solution at
this temperature.
[0140] 4. The main experiment was performed to assess whether or
not the polyelectrolyte (gelatin) participates in the interfacial
polymerization. A solution of gelatin (type A, 275 Bloom) at 0.5%
at pH 4.5 was prepared, brought into contact with the fragrance oil
containing 8% isocyanate, and the elastic shear modulus of the
interface G'i was measured. No amines were added to the water
phase, therefore the presence of 0.5% gelatin was the only
difference to the control experiment No. 1 described above in this
example. Surprisingly, after 30 minutes, increasingly strong values
of the elastic shear modulus of the gelatin/isocyanate interface
could be detected, and G'i steadily increased during the course of
the experiment. After 10 hours at a temperature of 45.degree. C.,
the modulus had increased to a value of 0.01 N/m. Additional
addition of free amines (3% guanazol) in the aqueous solution and
change of the pH to 11 further increases G'i. This experiment
demonstrates that gelatin is intimately integrated into the
composite, interlinked shell layer and that interfacial
polymerization already occurs between the gelatin and the
isocyanate, before additional free amines are added.
* * * * *